Morphological and Chemical Characterization of a Novel Wild Tea Plant Resource with Naturally Low Caffeine and High Theobromine from Guangxi Province, China

Zhuyecha (ZYC, Camellia sp.) is a newly discovered special wild tea plant resource in Cangwu County, Wuzhou City, Guangxi Province, China. However, there have been few scientific studies on it. This study investigated its morphological and chemical characteristics. The results revealed that ZYC is an arbor-type, upright plant with lanceolate leaves. The flower has five petals, five sepals, a trifid style, and a glabrous ovary. ZYC exhibited a unique chemical profile distinguished from common tea cultivars. Compared with the control cultivated varieties (Hongyan 12, Fuyun 6, and Yinghong 9), ZYC fresh leaves contained significantly higher contents of theobromine, theophylline, and gallic acid, but considerably lower caffeine and lower total catechins. The principal catechins were epi-form/galloylated catechins EGCG and ECG. Notably, theobromine was the most abundant alkaloid in ZYC, followed by caffeine and theophylline. In ZYC fresh leaves, 15 differential non-volatile metabolites were identified, and 22 key aroma compounds were screened, including linalool, (E)-2-hexenal, hexanal, heptan-2-ol, and β-myrcene, among others. The volatile components were primarily alcohols, aldehydes, and esters, contributing to floral, fruity, and green aroma attributes. This work enhances the understanding of the botanical and phytochemical properties of ZYC and provides scientific guidance for further research and efficient utilization of this natural low-caffeine/high-theobromine tea resource.